[DISCUSS] Only support official supported Ruby versions

[Antoine Toulme]

Hi all,

I would like to look into dropping all versions of Ruby except for the ones 
officially supported. Looking at MRI, this means 2.1.9, 2.2.5 and 2.3.1.
For JRuby, that is 1.7.25 and 9.0.50.

Does that make sense?

Cheers,

Antoine